Electronic equipment is being increasingly provided as portable electronic equipment, e.g., the so-called notebook-type personal computers, information terminals, video tape recorders, sound recorders and/or portable telephones, etc. and there are, e.g., electric bicycles provided with a motor for power assist, etc.
Such electronic equipment is adapted so that a battery pack (also called a battery package) is loaded into the equipment for the purpose of supplying power from the battery pack for operating the equipment.
An explanation will be given by taking the example of a notebook personal computer and battery pack therefor as an example of the prior art.
The function to detect whether or not a conventional battery pack is electrically connected to the body of the notebook personal computer be explained with reference to FIG. 1.
FIG. 1 shows a portion of the circuit configuration of an interface of a notebook personal computer 1000 and a battery pack 1002.
The notebook personal computer 1000 and the battery pack 1002 are detachably connected by a connecting portion 1003. A battery plus terminal (Batt+terminal) 1003a and a battery minus terminal (Batt-terminal) 1003e are connecting portions for power supply of the notebook personal computer 1000 and the battery pack 1002. The notebook personal computer 1000 can collect respective information of the battery pack 1002 such as charge/discharge current, battery voltage and capacity, etc. through a communication line from the battery pack 1002.
In FIG. 1, there is shown a communication system of the two wire type having a data line and a clock line, and the data line and the clock line of the notebook personal computer 1000 and the battery pack 1002 are respectively connected by a data terminal 1003b and a clock terminal 1003c. A B-IN terminal 1003d is a connecting portion of a detection line 1002e relating to the loading state of the battery pack 1002 in the body of the notebook personal computer 1000.
Reference numeral 1001a indicates a 5V power supply line of the notebook personal computer 1000, reference numeral 1001f indicates a communication LSI (Large Scale Integrated) Circuit of the notebook personal computer 1000, reference numeral 1001b indicates a pull-up resistor Rn 1 (e.g., 4.7 k.OMEGA.) of the data line, and reference numeral 1001c indicates a pull-up resistor Rn2 (e.g., 4.7 k.OMEGA.) of the clock line. Reference numeral 1001d indicates a pull-down resistor Rn3 (e.g., 10 k.OMEGA.) for allowing the loading state detection line 1002e of the battery pack 1002 to be at an L level (low).
Reference numeral 1002a indicates a 5V power supply line of the battery pack 1002, and reference numeral 1002f indicates a CPU (Central Processing Unit) for charge/discharge control of the battery pack 1002, communication with the notebook personal computer 1000 and various calculations. Reference numeral 1002d indicates a pull-up resistor Rp3 (e.g., 1 M.OMEGA.) of the loading state detection line of the battery pack 1002.
Let us consider the case where an AC adapter (A.C. current adapter) is not connected to the notebook personal computer 1000 and the 5V power supply line 1001a of the notebook personal computer 1000 has a high impedance. Before loading of the battery pack 1002 is detected, the CPU 1002f of the battery pack 1002 does not deliver power to the notebook personal computer 1000. When the battery pack 1002 is loaded, the signal level of the loading state detection line 1002e of the battery pack 1002 shifts from the H level (high) to the L level (low) by a resistor (Rn3) 1001d of the notebook personal computer 1000, and the CPU 1002f thus detects loading of the battery pack 1002. When such loading is detected, the battery pack 1002 delivers power to the notebook personal computer 1000.
In the case where the battery pack 1002 is taken out of the notebook personal computer 1000, the loading state detection line 1002e is disconnected from the pull-down resistor(Rn3) 1001d, and its signal level shifts from the L level to the H level by the pull-up resistor (Rp3) 1002d.
In the case where, for the purpose of reducing current consumption, the battery pack 1002 is not loaded into the notebook personal computer 1000, or in the case where the notebook personal computer 1000 is in a sleep state even if the battery is loaded, power supply to a portion of the circuit within the battery pack 1002 is interrupted to reduce current consumption.
The charge/discharge operation of the battery pack 1002 is effected by the loading state, when the battery is not loaded, the battery pack 1002 inhibits the charge/discharge operation, but when it is loaded, it enables charge/discharge operation if the battery pack 1002 in a normal state.
Detection that the notebook personal computer 1000 is in a sleep state during loading is carried out by allowing the CPU 1002f of the battery pack 1002 to detect that the signal level of the communication line is not changed for a predetermined time or longer.
The battery pack 1002 serves to apply a latch for overcurrent protection so that charge/discharge operation is disabled. However, in the case where overcurrent is detected, the latch for overcurrent protection is released when the battery pack 1002 is taken out from the notebook personal computer 1000.
Further, the loaded battery pack 1002 does not deliver power to the notebook personal computer 1000 until it recognizes that the battery pack 1002 has been loaded (it is in the chargeable/dischargeable state). In addition, in the case where the battery pack 1002 is taken out, it does not inhibit charge/discharge operation until it recognizes that it is taken out except for an extraordinary state such as overcurrent, overdischarge or overcharge, etc.
For the above reasons, the function to detect the electrical loading state with respect to the connecting portion 1003 of the battery pack 1002 is important.
Meanwhile, as shown in FIG. 1, the connecting portion 1003 between the notebook personal computer 1000 and the battery pack 1002 requires five terminals in total for the battery plus terminal 1003a, data terminal 1003b, clock terminal 1003c, B-IN terminal 1003d and the battery minus terminal 1003e. Accordingly, in the case where the battery pack 1002 is connected by the connecting portion 1003 with respect to the notebook personal computer 1000, unless these five terminals are electrically securely connected, it is impossible to adequately deliver power to the notebook personal computer 1000 from the battery pack 1002.
If the number of these terminals of the connecting portion 1003 can be reduced, particularly if the B-IN terminal 1003d can be eliminated, the number of output terminals at the connecting portion 1003 is reduced. Thus, the battery pack 1002 can be more reliably electrically connected with respect to the notebook personal computer 1000, and miniaturization of the connecting portion can be realized and there can result less unsatisfactory terminal contact.